Inkjet printers are used in numerous applications to print text and/or graphics by utilizing piezoelectric or thermal technologies to deposit inkjet ink on a print medium. The inkjet ink includes a colorant and an ink vehicle, which is typically an aqueous-based solution that includes water and a mixture of water-soluble, organic solvents. As used herein, the term “colorant” refers to a dye, a pigment, or a mixture of at least one dye and at least one pigment. The ink vehicle optionally includes buffers, surfactants, humectants, and biocides to achieve the desired properties of the inkjet ink.
To achieve photographic image quality, the print medium used in inkjet printing must be fast drying and resist smearing, air, light, and moisture. In addition, the print medium should provide good color fidelity and high image resolution. Print media with photographic image quality generally include multiple coatings on a substrate or photobase layer. The coatings are formed from inorganic or organic materials, such as inorganic particles or organic polymers.
Conventional print media used in digital printing are typically categorized into two groups: porous media and swellable media. Porous media generally have an ink receiving layer that is formed from a porous, inorganic oxide bound with a polymer binder. As used herein, the term “porous” refers to a material that has a significant amount of voids, capillaries, communicated holes, and/or fissures. In the porous media, physical porosity is present. Typically, the polymer binder is present from 1 percent by weight (“wt %”) to 50 wt %, such as from 1 wt % to 10 wt %. Inkjet ink is absorbed into the pores of the ink receiving layer and the colorant is fixed in the porous medium by mordants incorporated in the ink receiving layer or by the surface of the inorganic oxides. Porous media have a short drytime and good resistance to smearing because the inkjet ink is easily absorbed into the pores of the ink receiving layer. However, porous media do not exhibit good resistance to fade. As used herein, the term “fade” or “fading” refers to light fade, dark fade, and air fade. In addition, while some porous media are resist to water and humidity, many porous media do not exhibit this desirable property.
In swellable media, the ink receiving layer is a continuous layer of a swellable, polymer matrix. As used herein, the term “continuous” refers to a material that does not have physical porosity. When the inkjet ink is applied to a swellable medium, the inkjet ink is absorbed by swelling of the polymer matrix and the colorant is immobilized inside the continuous layer. Since the colorant is protected from the outside environment, swellable media have greater resistance to light and dark/air fade than the porous media. However, the swellable media generally have reduced smearfastness and a longer drytime than porous media.
To overcome the undesirable properties of porous and swellable media, fusible or sealable print media have been developed and continue to be researched. With a fusible print medium, heat and/or pressure is applied after printing to produce a printed image that has improved resistance to water, humidity, smearing, and fading.
Recording media having a photobase layer, an inorganic particle layer, and at least one porous resin layer have been disclosed. The resin layer includes heteromorphic microspheres that are formed from a thermoplastic resin. During printing, inkjet ink passes through the resin layer and into the inorganic particle layer, which absorbs the inkjet ink and fixes the dye to the recording medium. The recording medium is heated to convert the resin layer into a film by fusion-bonding the microspheres to one another. The recording medium is alleged to have improved waterfastness and resistance to weather.
In addition, recording media having a temporary substrate and an ink absorption layer have been disclosed. The ink absorption layer includes porous, thermoplastic polymer particles of a predetermined size and shape. After printing, the recording medium is heated to a temperature above the melting point of the thermoplastic polymer particles to convert the ink absorption layer into a film.
Fast drying, record media have also been disclosed. The record medium has a microporous layer formed on a planar supporting layer. The microporous layer utilizes thermoplastic polymers that form capillaries in the microporous layer. If the microporous layer is opaque, it is converted to a transparent layer by heat, pressure, and/or exposure to solvents.
It would be desirable to provide an improved fusible print medium that has the desirable properties of the porous and swellable media. The fusible print medium would have a short drytime and increased resistance to smearing, fading, water, and humidity.